Bioluminescence is light chemically produced by living organisms. Around 1,500 species of fish can emit light. Numerous species of bacteria, algae, jellyfish, and a bunch of other ocean dwellers can also glow. This ability to produce light from the body can be found in creatures from floating plankton on the surface to the deep-sea dwellers, most of which are bioluminescent.
Different species have different ways of creating and using the chemical reaction. Some examples:
- Angler fish grow luminescent bacteria in a part of their bodies that dangles down, and the glow attracts prey.
- Lanternfish have photophores, or light-producing organs; we think they use them for communication and courtship.
- Some dragonfish have photophores that produce a far-red light invisible to most other deep-sea creatures, and they use it like a spotlight to stealthily illuminate their prey.
- The spectral lights that come from certain algae are the result of a chemical reaction that happens when the algae gets disturbed at night. The light attracts predators, which can be more interested in eating each other than eating the algae.
- The firefly squid uses photophores to flash light and attract prey. It also uses counter-illumination, or light that matches the brightnes and color of the surrounding area, along it's underbelly, to help it blend in with the sea surface above it. This helps protect it from predators.